The KaiOS or Antitheft account helps you to protect your device in case it was lost or stolen. To set it up, please check the instructions posted here: Currently, you can only set it up from your device, although you can access its features from phone's Browser or desktop computer/laptop via the link:

It has two main options: 'Remote Lock' and 'Remote Wipe'. For more information on how to set it up, please consult this article:

You can also use 'Make ring' command to force your device to ring in case you think it was lost somewhere near you.

The KaiOS account is not associated with the KaiStore. You're free to use the stores' features even without setting up the account.